Patent Document 1 describes an air conditioning device for vehicle. The described device passes cold air from an evaporator to a heating heat exchanger side under the control of a first air mixing door and a second air mixing door, both of which are formed of sliding doors.
The cold air from each air mixing door is split to air passing through an interior of the heating heat exchanger, and air passing above the heating heat exchanger (vehicle ceiling direction) and air passing under the heating heat exchanger (vehicle floor direction) by bypassing the heating heat exchanger. The three types of split air are blown into a vehicle compartment from a defroster outlet toward a windshield, a face outlet toward a face of an occupant, and a foot outlet toward foot of the occupant.
According to the technique of Patent Document 1, air passing above the heating heat exchanger (vehicle ceiling direction) flows around to a downstream side of the heating heat exchanger and is heated by a downstream wall surface of the heating heat exchanger in some cases. Such heating may possibly give rise to a fluctuation of a temperature of air conditioning air blown into the vehicle compartment.
In the air conditioning device for vehicle of Patent Document 1 adopting an inside and outside air bi-level structure, in particular, a bypass cold air passage is split to an upper direction and a lower direction with the heat exchanger in between. Hence, when an interior of the vehicle compartment is cooled to a maximum extent from the face outlet, that is, during so-called FACE mode Max Cool, a large volume of bypass air passing above the heating heat exchanger (vehicle ceiling direction) may possibly flow into a space on a downstream surface side of the heating heat exchanger. Consequently, a large volume of air that has flowed into the space on the downstream surface side of the heating heat exchanger readily exchanges heat with the downstream wall surface of the heating heat exchanger.